The present invention relates to the prescription and/or dispensing of ophthalmic lenses, typically lenses for spectacles or sunglasses.
The prescribing and dispensing of ophthalmic lenses includes several discrete aspects. In general terms, the act of prescribing is the determination of a wearer""s required refractive power, such as the determination of the wearer""s requirements for near and/or intermediate addition power. Similarly in general terms, the act of dispensing usually includes not only the selection of a suitable lens design but also the selection of a suitable frame (both optically and aesthetically) and the physical act of fitting the frame to a wearer, and the lens design to the frame relative to the wearer""s reference position.
The method and system of the present invention have been found to provide particular benefits when used for dispensing that involves the selection of a suitable lens design for an individual wearer. However, it is to be appreciated that the present invention is not to be limited to only this aspect of dispensing, nor only to dispensing per se. Indeed, and as will be described in more detail below, the method and system of the present invention may also find beneficial uses in other dispensing aspects (and also in aspects of prescription), and may for example be useful for the custom generation of ophthalmic lenses to suit individual wearer""s needs.
In the last 10 years, the design of ophthalmic lenses has advanced to a stage where there are now several different lens designs available for each category of lens type, such as for single vision lenses and progressive lenses. Referring particularly to progressive lenses, there is thus available to a dispenser a large number of progressive lens designs that may be dispensed to a wearer, each of which would be suitable to meet that wearer""s prescription requirements.
However, it has been recognized that individual wearers have differing physical features (such as stature, physique and shape), and also have different visual behavioural patterns (such as head, eye and postural behaviour while reading). All of these differing elements thus result in different lens designs being suitable for different wearers.
It is believed that, to date, and particularly with the development of differing types of progressive lens designs, dispensers have typically only used intuitive reasoning for recommending one particular lens design over another. Alternatively, dispensers may simply have relied on the lens manufacturer""s own information.
It is an aim of the present invention to provide a method and a system that can be used on-site by a dispenser, at least to provide a recommendation for the selection of a suitable lens design from a group of known lens designs, preferably in a reasonably short period of time.
The present invention provides a method for prescribing and/or dispensing ophthalmic lenses for a wearer, the method including determining at least the wearer""s individual visual behavioural patterns, analysing the visual behavioural patterns to provide visual behavioural data for the wearer and manipulating the visual behavioural data to provide, a lens design recommendation suitable for use in providing the wearer with a suitable ophthalmic lens.
The manipulation of the wearer""s visual behavioural data may include the comparison of that data with optical attributes of a group of standard ophthalmic lens designs, and the subsequent selection therefrom of a standard ophthalmic lens that is suitable for the wearer. Such a comparison will ideally be made with respect to a predetermined relationship between visual behavioural patterns and the standard ophthalmic lens designs. In this respect, reference to the term xe2x80x98standardxe2x80x99 is to be understood to be reference to an ophthalmic lens or ophthalmic lens design that is in accordance with standard specifications, and has not been custom manufactured to the requirements of an individual wearer.
Alternatively, the manipulation of the wearer""s visual behavioural data may include the generation of a custom ophthalmic lens design, and the subsequent manufacture of a custom ophthalmic lens that is suitable for the wearer. The generation of such a custom ophthalmic lens design may or may not utilize predetermined relationships between the known visual behavioural data and standard ophthalmic lens designs.
The method of the present invention seeks to at least identify a wearer""s typical head movement and/or typical eye movement, and preferably to utilise a relationship between head and/or eye movement characteristics and the wearer""s suitability for a particular lens design. In a simple form of the invention that relates to the dispensing of progressive lenses, the method preferably relies on a relationship that categorises wearers as either predominantly head movers or predominantly eye movers, particularly during reading, in order to allow accurate selection of a suitable progressive lens.
In this simple form, a wearer who may be categorised as an eye mover may, for example, require a progressive lens that provides a wide range of clear vision in the near zone, as the eyes will generally rove across almost the full width of the near zone when reading. Indeed, an eye mover may possibly be a person who is not well suited to a progressive lens at all.
On the other hand, the eyes of a wearer who may be categorised as a head mover will generally only utilise the central portion of the near zone of a progressive lens (due to the compensating movement of the wearer""s head when reading), thus allowing the use of a more traditional progressive lens with a narrower near zone. Such a person is generally considered to be well suited to the use of a progressive lens.
Additionally, similar categorisations may be used to assist with frame selection, particularly in terms of lens size. For example, some ophthalmic lenses are relatively small in order to be fitted into fashionable frames. However, if a wearer is categorised according to the method of the present invention as an eye mover, a relatively small lens may present that wearer with viewing difficulties when their eyes rove across the full extent of the lens, especially when their eyes use the peripheries of the lens where there may typically be greater distortion and blur or rove past the frame boundary.
By utilising the method of the present invention, a dispenser will be able to recommend that the wearer not use frames that require such small lenses, or alternatively may recommend a specific lens that has been designed to have minimum peripheral distortion and blur.
Therefore, not only would the method of the present invention find use for the dispensing of ophthalmic lenses, but also in research areas for the development of lens designs that can cater for different wearer""s requirements in terms of them being predominantly head movers or predominantly eye movers.
Hence, the present invention also provides a method for prescribing and/or dispensing ophthalmic lenses for a wearer, the method including determining at least the wearer""s individual visual behavioural patterns in terms of head movement and/or eye movement, processing those patterns with respect to a predetermined relationship between known head movement and/or eye movement characteristics and available ophthalmic lenses, such that the processing categorises wearers into a head movement or eye movement category that can then be used to produce a recommendation for an ophthalmic lens for the wearer.
Furthermore, and in terms of the present invention being embodied in suitable apparatus, the present invention additionally provides a system for prescribing and/or dispensing ophthalmic lenses for a wearer, the system including means for determining at least the wearer""s individual visual behavioural patterns, means for analysing the visual behavioural patterns to provide visual behavioural data for the wearer and means for manipulating the visual behavioural data to provide a lens design recommendation suitable for use in providing the wearer with a suitable ophthalmic lens.
In this form of the invention, the means for determining at least the wearer""s individual visual behavioural pattern further includes means for sensing the wearer""s head position, means for formatting the wearer""s sensed head position in the form of wearer""s sensed head position data, means for storing the wearer""s sensed head position data and means for processing the wearer""s sensed head position data.
In yet another form of the invention, the means for determining the visual behavioural pattern further includes means for sensing the wearer""s eye position, means for formatting the wearer""s sensed eye position in the form of wearer""s sensed eye position data, means for storing the wearer""s sensed eye position data and means for processing the wearer""s sensed eye position data.
Ideally, the means for sensing the wearer""s head position and the means for formatting the wearer""s sensed head position as head position data are provided by a single piece of equipment referred to as head tracking apparatus.
In an alternative form, the means for sensing the wearer""s eye position and the means for formatting the wearer""s sensed eye position as eye position data may be provided by a single piece of equipment referred to as eye tracking apparatus.
The present invention also provides a system for prescribing and/or dispensing ophthalmic lenses for a wearer, the system including means for determining at least the wearer""s individual visual behavioural patterns in terms of head movement and/or eye movement, means for processing those patterns with respect to a predetermined relationship between known head movement and/or eye movement characteristics and available ophthalmic lenses, means for categorizing the wearer into a head and/or eye movement category and means for recommending an ophthalmic lens for the wearer corresponding to the wearer head and/or eye movement category.
It will thus be recognised that the method and system of the present invention aim to match a wearer to a lens design (and vice-versa), rather than to force a wearer to adapt to a lens design. In this respect, when a new lens is worn for the first time, or when a lens design is changed, or when a new lens design is introduced to the market, wearers have traditionally been forced to modify their visual behavioural patterns. This usually results in a difficult period of time for a wearer (particularly a wearer whose visual behavioural patterns are not well matched to the new lens design), which will often result in rejection of a particular lens type and possibly even failure of a new lens design on the market.
However, by utilising the method and system of the present invention, a dispenser can ensure that wearers are fitted with lens designs that suit the wearer""s visual behavioural patterns, thus avoiding rejection of a new lens design simply because of an inappropriate matching of a lens design to a wearer, and also minimising any difficult introduction period. Indeed, the method and system of the present invention are capable of analyzing various of the physical, and/or optical and/or environmental characteristics of an individual wearer, and either relating those characteristics to known categories of lens designs, and subsequently recommending for the dispenser a suitable lens design selected from a group of known lens designs, or for making a custom lens design for an individual wearer, which custom lens design is based upon the analysis of the various characteristics.
A wearer""s individual visual behavioural patterns may be determined in any known way, although it is preferred to do so in a manner that at least produces data that may be used to determine whether a wearer can be categorised as a head mover or an eye mover when tested during near and intermediate viewing.
In one form, this may require use of a spacial motion tracking system that is capable of recording head position and reading material position information. From this information, both reading ergonomics (such as head tilt, head rotation, and reading material distance and angle) and eye movement data may be calculated. The data may then be displayed and analysed such that wearers can be categorised on the basis of at least head movement, eye movement and posture, which in turn can be used to recommend lens designs, lens product categories, frame/lens combinations, or lens prescription.
In a preferred form of the present invention, the recording of data, the processing, display and analysis of that data, and the provision of a subsequent recommendation, are all functions that are performed by a computer.
In this respect, the data to be gathered and recorded from a wearer may be quite varied, and will be somewhat dependent upon the expected use for any particular system that utilises the present invention. For example, while the method of the invention will most likely be required to take into account various optical characteristics of the wearer, such as the nature and type of a wearer""s current lens design and prescription, and the wearer""s prescription status (namely, myope, emmetrope or hyperope), together with the characteristics referred to above as visual behavioural patterns, other external factors may also be taken into account.
While the gathering and recordal of any external factors, as well as the optical characteristics mentioned above, will most likely be a simple matter of manual data entry, gathering and recordal of the visual behavioural patterns of a wearer will generally require more than that, and may require monitoring and/or measurement of the wearer to determine various elements, with subsequent analysis and calculation to determine further elements.
For example, the visual behavioural patterns that care preferably utilised in the method of the present invention will most usually be embodied in head movement and/or eye movement when a wearer views a subject (such as when reading). Whilst head movement may be relatively easy to detect and measure, eye movement typically will not be. Thus, in a preferred form of the present invention, characteristics of head movement and eye movement may be determined by measuring elements that can be referred to as visual ergonomics, such as wearer""s head tilt, head rotation, and reading material distance and angle.
By gathering and recording such visual ergonomic data it is possible to calculate a wearer""s eye movements. There should subsequently be sufficient information from which to determine if a wearer should be categorized as an eye mover or a head mover, if that is the categorisation required to achieve the dispenser""s aim for the method of the present invention.
With regard to the relationships that assist in categorising wearers, it must be appreciated that these relationships are generally to be determined in accordance with the dispenser""s aims for the method being used. For example, if the method of the present invention is being used to provide recommendations for particular progressive lens designs, then it is expected that the categorisation of wearers as head movers or eye movers will suffice. However, it will be appreciated that this will require a determination to have been made as to a degree of head movement and a degree of eye movement below or above which a wearer will be appropriately categorised.
For example, it may be acceptable to define low, medium and high amounts of head turn (in degrees) together with low, medium and high amounts of eye declination (in degrees) when a wearer is tested using a spacial motion tracking system as will be described below, by determining arbitrary cut-off values in accordance with statistical populations. Thus, the processing of the data gathered and recorded by such a spacial head tracking system may simply provide as an output the location of a wearer""s visual behavioural patterns in a matrix such as in Table 1 below, where the five asterisks identify a sample location:
In this example, where the dispenser is aiming to match a wearer to known types of progressive lens designs, a relationship between the matrix of Table 1and the available types of progressive lens designs will also need to have been predetermined. A sample product recommendation table may be as follows in Table 2:
As will be appreciated, in this example, the dispenser would recommend to the wearer that progressive lens type D would best suit that wearer""s visual behavioural patterns, suitably weighted with influence from any of the other external and environmental elements and optical characteristics mentioned above, as necessary. In this respect, such weighting will preferably be included in either the analysis of the data to result in placing the wearer in a particular location in Table 1, or possibly in the determination of the alignment of particular lens types to particular locations in the matrix of Table 2.